Real Estate - Dispositions (Details) - Disposal Group, Not Discontinued Operations [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price	$ 153,750
Gain on Sale	81,965
Fund III [Member] | Cortlandt Towne Center [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price	107,250
Gain on Sale	65,393
Fund III [Member] | Heritage Shops [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price	46,500
Gain on Sale	$ 16,572